Nuclear localization of p27KIP1 is induced by scavenging hydrogen peroxide in tumor cells

IBAÑEZ, IRENE L.; BRACALENTE, CANDELARIA; ROJAS, PAOLA; POLICASTRO, LUCÍA; TROPPER, IVANNA; MOLINARI, BEATRIZ; DURÁN, HEBE

Santiago

Congreso; Free Radicals and Antioxidants in Chile. VI Meeting of the Society for Free Radical Biology and Medicine (SFRBM) South American Group; 2009

Society for Free Radical Biology and Medicine (SFRBM) South American Group

Reactive oxygen species (ROS) are involved in the regulation of proliferation. We previously demonstrated cell cycle arrest by scavenging H2O2 in tumor cells, which was mediated by the modulation of the regulatory proteins of G1/S, cyclin D1 and p27KIP1. The aim of the present study was to evaluate the regulation and intracellular localization of the inhibitory protein p27KIP1 in different types of tumor cell lines in response to different levels of H2O2. The PIG-1 (melanocytes), A375 (melanoma) and LoVo (colon carcinoma) human cells and the CH72-T4 (spindle-cell carcinoma) murine cells were used. To modulate the intracellular levels of ROS, cells were stably transfected with cDNA of human catalase or Cu,Zn-SOD. ROS levels were determined by DCFH-DA assay and cell cycle analysis was performed by flow cytometry. Cyclin D1 and p27KIP1 were determined by western blot and the intracellular localization of p27KIP1 was analysed by immunocytofluorescence. Results showed a correlation between the levels of endogenous ROS and cyclin D1 expression. H2O2 scavenging induced an increase in p27KIP1 and a modification in its intracellular localization. High levels of p27KIP1 were found in the nucleus after lowering H2O2 levels as compared to proliferating control cells, which showed lower levels and cytoplasmic localization of this protein. Cancer cells frequently show low levels or mislocalization of p27KIP1 protein. We suggest that this deregulation could be explained by the permanent shift in the redox status, characteristic of cancer cells, which would in turn be responsible for activating ROS-dependent signaling involved in the regulation of p27KIP1.